Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/15

Rh AYD AYES OF NORTII AMERICA. 11 readily deteimined. When the postorbital roof bone is raised up, the meeting of two gular dermal banes, as I interpret them, is seen. One of these is a plate directed backwards and outwards, bearing minute radiating lines on its upper surface. It meets a similar flat plate directed forwards and outwards with similar lines radiating to the circumference. The inner margins of these plates were not seen. The orbits are remarkably small, and situated probably near the middle of the longitudinal measurement of the cranium. The external snares are not defined, but symmetrical depressions in the position they usually occupy in Salamanders aie distinct. The general form recalls Menopoma, particularly the small orbits. A slender curved bone with a slightly dilated and truncate extremity, lying by the cranium in connection with the inaudible, is like a branchihyal of that genus. Neverthekss it cannot be positively assigned to that genus, as numerous cycloid scales of fishes are on the same block. PARIOSTEGUS MYOPS, Cope. The surfaces of the cranial bones are little sculptured ; there are small tnbcrculiform elevations on the parietal and more numerous ones on the preorbitals. The postorbitals show the strongest markings of elongated pits, which radiate to their circumference, leaving a smooth obtnse border. The nasals present a series of small warts at a little distance on each side of their common suture, and transverse to it. The surface of the maxillary is marked with longitudinal grooves and shallow pits. No suture separating maxillaries and premaxillarics can be traced with certainty, though the bones of the jaw are interrupted at the usual place of suture, opposite the nostril. Measurements. Lines. Length of specimen (including mandible), 18 Width between outer convexities postorbitals, 17 Do. do. inner borders orbit, 11 Do. of same without preorbitals, 8 Do. of nasals at middle, 2.5 Do. of orbit, 1.5 Length of frontal and nasal premaxillary, 11 Do. of supposed branchiliyal, 12 The name is derived from the roof-like postorbitals with free lateral margin. LOCALITY. Coal bed of the Keuper Triassic, Chatham county, North Carolina. The species was discovered b3 Prof. Jos. Leidy, who handed it to me for description. It is in the Museum of the Academy Nat. Sciences of this city.